The objective of this proposal is to investigate the use of MYXV as potential oncolytic virotherapy agent against pancreatic cancer in preclinical animal models. The proposal focuses on MYXV, and is based on our previously published reports and supporting preliminary studies. MYXV is a rabbit-specific poxvirus with oncolytic activity against many types of human cancer models in vivo, including brain tumors, melanoma and rhabdoid tumors. In addition, we reported recently that MYXV is able to infect and kill pancreatic cancer cells in vitro. Our preliminary studies provided in the main body of the proposal show that MYXV exhibits potent oncolytic activity in both immunodeficient and immunocompetent animal models of pancreatic cancer. Based on these results, we seek to evaluate MYXV in combination with current chemotherapy regimens, especially gemcitabine, for pancreatic cancer. We hypothesize that MYXV will have potent oncolytic activity against pancreatic cancer in vivo and may be combined and/or engineered to enhance current chemotherapy treatments. Wildtype MYXV and recombinant MYXV armed with chemosensitizing gene(s) will be evaluated as single agent therapies and in combination with current chemotherapy drugs approved for the treatment of pancreatic cancer. For the purposes of this grant, we propose to: 1) Evaluate the efficacy of wildtype MYXV oncolysis in murine models of pancreatic carcinoma. MYXV will be evaluated: a) as a single agent therapy compared to standard chemotherapies, b) in combination with gemcitabine and/or erlotinib, and as c) second line treatment therapy for chemotherapy resistant tumors. These experiments involve the use of the most common first line chemotherapies for pancreatic cancer and will therefore evaluate MYXV in the context of a clinically relevant scenario. Immunodeficient and immunocompetent murine models of pancreatic cancer will be established intraperitoneally (IP) and virus will be administered locally by the IP route. Tumor burden and survival curves will be compared between treatment groups in the presence or absence of gemcitabine and in gemcitabine refractory tumors to determine if MYXV virotherapy under the three regimes mentioned above results in an enhancement of therapeutic benefits as measured by tumor burden and survival. 2) Generate recombinant MYXV armed with chemosensitizing genes that will enhance gemcitabine-based chemotherapy. Recombinant armed MYXVs that express deoxycytidine kinase (CDK) or the human equilibrative nucleoside transporter 1(hENT-1) will be engineered. These viruses will be characterized in vivo to determine if the expression of the transgenes enhances gemcitabine-based oncolysis of pancreatic cancer cells in the two models described above in Specific Aim 1. Tumor burden and survival curves will be compared between armed and wildtype MYXVs treated groups to determine if the use of an armed MYXV provides a therapeutic advantage over wildtype MYXV by enhancing gemcitabine-based chemotherapy in vivo. This proposal will be the first study to evaluate the oncolytic potential of MYXV in preclinical animal models of pancreatic cancer as single agent therapy and in combination with chemotherapy drugs, as well as the characterization of armed MYXV capable of sensitizing cells to gemcitabine chemotherapy. Thus, if successful, these pilot experiments will identify MYXV as an effective oncolytic virus that can be further developed as a novel, safe virotherapy for the treatment of pancreatic cancer. In particular, if the results are as positive as we anticipate, and given the excellent safety profile of MYXV, we will pursue the production of clinical grade stocks of MYXV and the filing for an investigational new drug application (IND) at the completion of the proposed study.